The ability of a pneumatic tire to run when it is entirely deflated, while always an important factor, has become an increasingly important factor in the design of pneumatic tires. A great deal of emphasis is now being focused upon this characteristic of a tire due to the effort to conserve out scarce raw materials, the effort to eliminate the spare tire in an automobile and the effort to provide a stable, safe tire construction which can withstand the rigors of being run uninflated for at least a certain distance at a certain minimum speed without destroying the remaining useful life of the tire.
In a prior application (Ser. No. 545,263, filed Jan. 30, 1975) one of the applicants disclosed an improved tire construction designed to facilitate the run-flat characteristic of a tire. This construction comprised a bead latch which is located in the lower sidewall area of the tire radially outwardly and above the position of the rim flange when the tire is mounted on a rim. A substantial portion of the bead latch extends axially outwardly beyond the rim flange for a substantial distance and a portion of this axially outwardly extending portion extends radially inwardly of the rim flange. The bead latch thereby completely engulfs the rim flange. This novel construction prevents the bead from unseating when the tire is run flat, thereby preventing the tire from extensive damage during run-flat operation and yielding a stable run-flat tire which can be driven without undue danger of losing control of the vehicle.
Often when the tire is run under normal conditions of pressure and load, and particularly when the tire is run flat, the bead latch is in contact with the rim flange and an abrasion of the bead latch results which eventually will render the bead latch inoperative; that is, the bead latch will abrade to such an extent that it will not prevent the tire bead from unseating when the tire is run flat. The present invention eliminates a significant amount of this abrasion damage by enabling the bead latch to operate independently of the tire body so that the severe deflection of the tire body is not directly transmitted to the bead latch.
The present invention is an improvement in the bead latch construction disclosed in the above identified prior application. This improvement consists of incorporating means into the bead latch which enables it to act independently of the tire body. This permits the bead latch to perform its function while the tire body is severely deflected without putting a severe load on the bead latch. This mitigates any severe chafing which may occur in prior bead latch constructions.
The decoupled feature of the bead latch of this invention which results in the independent action of the bead latch may be obtained by several ways; by incorporating a circumferential groove in the bead latch, by incorporating a series of radially disposed grooves in the bead latch or by incorporating a combination of the circumferential groove with a series of radial grooves in the bead latch.
The decoupled bead latch facilitates mounting and dismounting of the tire without harming the functionality of the bead latch itself. The primary advantage of the decoupled feature of the bead latch is to lessen the amount of abrasive wear which the periphery of the bead latch encounters when it is touching the rim flange during normal operation and, particularly, when the tire is run flat.
It is an object of this invention to provide a bead latch construction which mitigates the abrasive wear which occurs to the bead latch when the tire is run under normal conditions or run flat.
It is a further object of this invention to provide a bead latch which operates independently of the tire body.
Other objects of the invention are evidenced by the disclosure of the specifics of this construction which follows.